For nearly 100 years, fluid collection cards containing a solid phase matrix for the collection and subsequent analysis of a dried specimen matrix have been used as a scientific tool. For example in the early 1960s, Dr. Robert Guthrie used filter paper to collect dried blood spot specimens to measure phenylalanine in newborns for the detection of phenylketonuria (Guthrie and Susi 1963). This application for collecting blood led to widespread screening of newborns for the detection of treatable, inherited metabolic diseases. Typically, a patient's fingertip is punctured and the card is impregnated with blood from the puncture site. The blood is allowed to dry and the card is then sent to a testing laboratory. At the testing laboratory, a portion of the card impregnated with blood is separated, such as cut out or punched out, producing a coupon from which the blood is eluted. The eluted blood may then be analyzed for compounds contained within the blood specimen.
Presently, a wide variety of fluid collection cards are available for purchase. Conventional collection cards typically consist of a single layer filter paper containing printed indicia on one side. Like most standard scientific devices, card devices typically have an associated imprecision. The imprecision associated with conventional collection cards may be related to many factors, including:                a. the filter paper's consistency and quality,        b. unknown changes that may have occurred to the filter paper,        c. lack of proper spotting technique; and        d. the addition of printed indicia,        e. specimen contamination or damage during handling, processing, or transportation.        
Conventional fluid collection cards typically contain a standardized filter paper made from high purity cotton linters, and manufactured to maximize the accuracy and precision with which specimens are absorbed. If used properly, the card devices may provide an acceptable level of accuracy and precision for a given application, for example like those that analytical scientists and clinicians have come to expect from standard methods of collecting blood, such as capillary pipettes.
Because a large surface is exposed on the sample collection area, conventional fluid collection cards are easily contaminated by the user, for example, contact with hands or some other surface prior to sample collection often introduces hand lotions alcohol, body oils, or DNA contamination. This contamination may interfere with the proper absorption of the fluid into the filter paper and therefore may interfere with the accuracy of the volume or content of the sample collected.
The manufacturers of the available card devices emphasize the importance of proper spotting technique, or proper specimen collection technique, and the consequent impact on specimen quality. For example, if the patient's finger touches or is smeared across the absorbent material of the collection card, the full volume of the material is not filled with specimen (i.e., the volume of the absorbent material through to the back of the material is not filled); therefore, when punched, results in a coupon with an inaccurate volume of specimen and consequently an inaccurate analytical result (i.e., concentration of analyte in specimen). In order to obtain an accurate volume specimen, ensuring the filter paper is filled thoroughly to the back of the paper without over filling and not on the surface alone is essential. With the conventional fluid collection cards, however, the imprecision introduced as a result of mishandling by the user, is difficult to control.
In conventional collection cards, indicia have been printed upon the exposed surface of the card, which indicated where on the card to apply the fluid specimen. These printed indicia may interfere with the uniformity of absorption of the specimen into the paper material. The ink or pressure applied during printing can change the density of the material and may cause the specimen to slow or hasten during the spreading processes which will lead to an inconsistent final volume of specimen per coupon.
Because the specimen is contained on an exposed surface, it may become contaminated or otherwise damaged during handling or transport. To overcome this problem improved collection cards comprise a protective housing. For example, collection cards used in the HIV and Hepatitis C Home Test Systems available from the Home Access Health Corporation of 2401 West Hassell Road, Suite 1510 Hoffman Estates, Ill. 60169, and sold under the trademark HOME ACCESS, comprise a matchbook type housing. Similar housing is commonly used to transport biological specimens as disclosed in U.S. Pat. No. 4,225,557 to Hartl et al. and U.S. Pat. No. 4,789,629 to Baker et al. Although, the use of such packing increases production costs it provides needed functionality.
The use of fluid collection cards still has many advantages including, ease of collection, transport, and storage, making them a cost-effective choice for certain applications.